1. Field of the Invention
The present invention relates to an optical scanner that scans a light beam, and particularly to an optical scanner employed in the scanning device of an electrophotographic image-forming device.
2. Description of Related Art
Electrophotographic image-forming devices, such as laser printers, employ an optical scanner (scanning device) to emit a beam of light onto a photosensitive drum, enabling the exposed regions of the drum to carry a toner image. The toner image carried on the photosensitive drum is subsequently transferred onto a recording medium, such as paper or a transparency, forming an image thereon.
The optical scanner is configured of a light source, and optical members, such as mirrors and lenses, for deflecting the light emitted from the light source and for guiding the light toward the photosensitive drum.
If the mounted angles of the optical members are inexact, the light will not be irradiated onto the photosensitive drum parallel to the axis of the photosensitive drum but will be slanted or curved, making it impossible to guide the light beam to prescribed positions on the photosensitive drum. Consequently, the quality of the images formed on a recording medium will degrade.
Therefore, technologies such as that disclosed in Japanese unexamined patent application publication No. 2001-215434 have been proposed for adjusting the mounted angles of the mirrors. An angle regulating screw with a tip contacting the mirror is rotated to adjust the protruding length of the screw, thereby adjusting the mounted angle of the mirror. The regulating screw also maintains the mirror at this mounted angle.
However, due to manufacturing irregularities within the range of tolerance, play similar to the backlash in a gear mechanism is produced between the external threaded part of the screw (male screw) and the internal threaded part (female screw) through which the male screw is inserted. Hence, even after adjusting the mounted angle of the mirrors with the technology disclosed in Japanese unexamined patent application publication No. 2001-215434, the angle regulating screw cannot maintain the adjusted angle due to the play produced between the male screw and the female screw.
Although this problem of play produced between the male and female screws can be reduced by increasing the manufacturing precision in the screw parts, such an increase in manufacturing precision leads to a rise in costs for manufacturing the angle regulating screw.
Further, while in theory the protruding length of the regulating screw changes continuously in proportion to the rotational amount of the screw, in reality this does not occur due to the play between the screw parts. In other words, the protruding length of the regulating screw varies discontinuously relative to the rotational amount of the screw.
Hence, since the invention in Japanese unexamined patent application publication No. 2001-215434 cannot maintain the mirrors at a desired mounted angle, this technology cannot maintain optical members, such as mirrors and lenses, at suitable mounted angles.
Further, if the surface precision in the part of the regulating screw that contacts the mirror or if the surface precision in the part of the mirror that contacts the regulating screw is low, the optical members cannot be maintained such that the mounted angle of the mirrors is suitable.
While this problem can be resolved by increasing the surface precision in these contact areas, this resolution also leads to an increase in manufacturing costs for the regulating screw and mirror.
Further, dust buildup on mirrors, lenses, or other optical members is a primary cause of poor performance in the optical scanner. Poor performance caused by such dust buildup can be resolved by removing the optical members from the frame and cleaning the members.
However, the regulating screws must be loosened in order to remove the mirrors or other optical members in the invention disclosed in Japanese unexamined patent application publication No. 2001-215434. When the optical member that was removed and cleaned is subsequently remounted on the frame, the mounted angle of the optical member must be readjusted, even when the member is being mounted on the same frame. Accordingly, the invention disclosed in Japanese unexamined patent application publication No. 2001-215434 is not suited for reassembling the optical scanner. That is, maintenance of the optical scanner is not facilitated with this technology.